Alternating-current motor



May 25 @1925; 1,586,231".

H. WEICHSEL ALTERNATING CURRENT MOTOR Filed May 21, 1924 wmn B Patented May 125, 1926.

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ALEEBNATING-CUERENT MOTOR;

Application filed lay :1, 1m. semi Ra. mm;

- My invention relates to means for and method or? starting an alternating current motor of the self-excited synchronous type.

w revolvin Among the objects of my invention are to eliminate polyphase currents from the commutator at starting and thus avoid commutation dificulties which these may cause, and

to reduce the resistance of the secondarystarting circuits to the lowest possible, value whereby a maximum induction motor speed (minimum slip) may be attained, by the machine rior to makin the connections whereby t e machine may e caused to operate as a chronous'motor.

Referring to the accompanying drawing showing the embodiment of my invention the motor, when-operating as a synchronous machine, comprises an inducing member which, in the machine illustrated, is the member, provided with a polyphase winding 1 supplied with polyphase currents through slip rings 2,3 and 4. The induced member is also provided with a commuted windin 5 which may be interconnected with t e polyphase winding if desired, and with brushes 6-7. carries an exciting windin 8 in circuit with these brushes and displace by a small angle from the brush axis. derstood, the E. M. F. appearing at the brushes 6'? is a direct current E. M. F. at synchronous speed, the winding 8 on which t is E. M. F. is impressed supplies the necessary unidirectional excitation of the machine. The slight displacement of the axis of the winding 8 from the brush axis results in one component of the exciting magnetization being so located as to satisfactorily influence the power factor of the machine and vet this an lar displacement is referably hept small in order that the windlng 8 may be in position to contribute to the develo .nent cf a good synchronizing torque shou d the machine be temporarily pulled out of step by over load. I

Referring to the means for starting the machine described, the stator is rovided with a windin 9 axiall dis laced rom the winding 8 an ada te to e closed on itself through adjusta le resistance 10. Means including the conductor 11 and the switch 12 are also provided for closing the winding 8 on itself at starting over adjustable resistance 13. The switch 12 is provided with The stator position the switc Since, as is well un-- contacts 14, 15 and 16 and is adapted, to

interconnect contacts 15 and 16 in oneof its positions, and contacts 14 and 15 in another position. A resistance 17 is included in circuit between the brush 6 and the contact point 15. v v

.To start the machine described, resistances 10 and 13 are set at a suitable value and switch 12 is located in the position shown in full lines in'the drawing where, through contact 16, it establishes a closed circuit through windin 8 and the brush circuit 1. left open. Po ypliase current being supplied to the slip rlngs, currents are induced in the'windin s 8 and 9 and the machine starts as an in uction motor. The resistances 10 and 13 can then be reduced in one or more steps and preferably the winding 9 is short-circuited. When the machine hasreached its maximum induction motor speed which, unless the machine is over loaded, will closely approach the synchronous speed in my machine, the switch 12 is moved to its running position in which,

through contact 14, it laces the brushes in circuit, with the win ing 8. In moving from the starting position to the running interconnects contact points 15 and 16, before passing ofi' contact 16, and therefore before placing the conductor-ll in open-circuit. At maximum induction motor speed the induced current flowing in'the conductor 11 is in the o po- I site direction to the current which .wi be delivered from the commutator when contacts 15 and 16 are interconnected, and by suitably proportioning the resistance 17 the current in conductor 11 can be made substantially zero at the time this conductor is I open-circuited and therefore sparking at this time, when the switch is moved rom starting to running position, will be avoided.

applicable to single phase as well as polyits phase motors and to machines in which the inducing and commuted windings are on the stationary member.

Havin fully described my invention, what I c aim as new and desire to secure by Letters Patent of the United States is:

Inen alternatin current motor, the combination of an in min member provided with e commutator and slip rings, an induced member provided with an excitin winding and o second Winding displeceg therefrom and closed on itself, switching means associated with the exciting Winding, said means bein adapted when in one position to connect t e exciting winding in series with the commutator and in another position to disconnect it from the commutator and close it on itself, and means for including a resistance between the commutator and a conductor forming part of the means forming a closed circuit through the excitinq winding, said resistance being proportioned to limit the current delivered by the commuted Winding to substantially the same value as the induced current flowing through the excitin Winding.

In testimony whereof, I have hereunto set my hand this the 15th day of May, 192

HANS EICHSEL. 

